1. Field of the Invention
The present invention relates to a noncontact IC device, such as a noncontact IC card, capable of exchanging data with an external reader/writer in a noncontact communication mode and, more particularly, to a noncontact IC device capable of being easily changed from an unused state to a used state.
2. Description of the Related Art
IC cards provided with terminals have prevalently been used particularly in France as prepaid telephone cards because of their high ability to prevent the dishonest alteration of information stored therein as compared with magnetic cards.
It is difficult to discriminate between a used state and an unused state of a prepaid IC card provided with terminals, like a telephone card. Unused prepaid IC cards must be identified not only by coupon shops but also by purchasers.
Prepaid telephone cards having 0.25 mm in thickness of a magnetic recording system are used in Japan. The start of use of this prepaid telephone card and an approximate number of remaining message units are indicated by holes formed by punching in the telephone card. Generally, the thickness of IC cards is as great as 0.76 mm. Therefore it is not easy to punch holes in IC cards and IC cards are not used as prepaid telephone cards.
When an IC card provided with terminals is used as a telephone card, the IC card sealed in a film envelope is sold, and the film envelope is cut and the IC card is taken out of the film envelope when the IC card is used for the first time. Thus it is considered that an IC card wrapped in an unsealed film envelope at the least is not an unused IC card and that an IC card perfectly sealed in a film envelope is an unused IC card.
Noncontact IC cards capable of sending data to and receiving data from an external device in a noncontact communication mode by using electromagnetic radiation have been used in recent years. The noncontact IC card does not need to be physically connected to an external device by using contacts, which is needed by the IC card provided with terminals. Since the noncontact IC card exchanges radio messages with the external device, the noncontact IC card sealed in an envelope can be used without being taken out of the envelope. Accordingly, it is impossible to discriminate between a used state and an unused state of the noncontact IC card wrapped in an envelope only from the condition of the envelope. The noncontact IC card may be wrapped in an envelope having an electromagnetic shielding effect to enable the discrimination between a used state and an unused state of the noncontact IC card from the condition of the envelope, which, however, is expensive and is incapable of preventing the dishonest selling of used noncontact IC cards wrapped in a false envelope similar in appearance to a genuine envelope at coupon shops.